Heart valve replacement is a common procedure for patients suffering from heart valve damage due to a variety of ailments and disease. Prosthetic heart valves comprise two main types, mechanical and natural tissue valves. Mechanical replacement heart valves comprise a mechanical apparatus usually made from metal or plastic having mechanisms to allow flow in one direction and resisting flow in the opposite direction. An example of a mechanical heart valve is described in U.S. Pat. No. 6,645,244 for MECHANICAL HEART VALVE PROSTHESIS to Shu, et al and assigned to the assignee of the present application. In the '244 patent, flow enabling leaflets are supported for pivotal movement in an improved design to wash the hinge recess to increase the life of the valve.
Natural or Biosynthetic heart valves are made by using a tissue valve from a large mammal (porcine, bovine, equine). These natural tissue valves are removed from the animal, and chemically fixed to preserve the tissue to prevent rejection by the patient. The natural tissue valve is usually enhanced with support and attachment devices. The tissue valve comprises movable tissue flaps called leaflets to control the directional flow of blood. An example of a prior art tissue valve is described in U.S. Pat. No. 5,549,665 to Vesley et al. entitled, BIOPROSTETHIC VALVE. In the '665 patent a valve made of natural tissue is mounted on a stent having commissure posts and a sewing ring. The stent is covered with a biocompatible material.
Both mechanical and natural prosthetic valves may use a sewing ring at the inlet of the valve structure and a stent surrounding the valve. The surgeon attaches the valve to the patient by suturing the sewing ring to the annulus of the valve to be replaced. The stent of a natural prosthetic valve comprises commissure posts extending circumferentially from the sewing ring and around the outlet of the valve. The stent supports tissue around the valve to allow the valve to control the flow of blood. The stent helps the leaflets move by holding surrounding tissue spaced from the valve.
A valve holder is removably connected to the stent or sewing ring to hold the valve during placement in the patient. The physician performing the valve replacement, attaches a handle to the valve holder to remove it from the packaging and prepare for insertion. The valve is held in a position outside the annulus during the initial placing of the valve sutures. The valve may be oriented for optimum performance, for example, aligning the largest inter-commissure space with the right fibrous trigone. The valve sutures are individually threaded onto the annulus of the patient's defective valve and extended to a corresponding position on the outer portion of the sewing ring of the replacement valve. The valve sutures prevent leaking around the sewing ring by close spacing around the entire perimeter of the heart valve. The valve sutures are placed so as to create an orderly array or web connection around the entire valve. Accessibility of the entire circumference of the sewing ring for suture placement is desirable. The physician must be careful to engage only the sewing ring on the prosthetic valve. Suture entanglement with the holder, or the stent creates a loose connection. Furthermore, care must be taken to not entangle or suture the leaflets during the connection process.
The valve sutures must avoid the holder sutures attaching the holder to the sewing ring and especially the knots terminating the holder sutures. Entanglement of the valve sutures with the holder, holder sutures or holder suture knots could cause paravalvular leakage when the holder is removed after the valve has been secured. The connection between the holder and the sewing ring should be isolated from the valve sutures to avoid entanglement.
Thus, visibility of the sewing ring and the leaflets is important during the attachment process. The handle and the holder in prior art designs block visibility along the axis of the valve making suture entanglement difficult to avoid. In attaching a mitral valve for example, the leaflets and stent are distal to the handle and difficult to observe with prior art designs. An example of a prior art holder where visibility is limited is described in U.S. Pat. No. 5,776,187 for COMBINED HOLDER TOOL AND ROTATOR FOR A PROSTHETIC HEART VALVE to Krueger et al. In the '187 patent, a holder is described that partially blocks visibility of the outer portion of the sewing ring and further blocks visibility along the axis of the valve through the sewing ring. Visibility of the sewing ring is critical to assure the sutures are well placed. Visibility past the holder into the area of the leaflets helps the physician avoid entangling the leaflets with the valve sutures. Preferably, the valve leaflet should be visible through the interior of the sewing ring.
In addition to visibility, tissue accessibility is also important. Access to the tissue from both the inflow and outflow sides of the valve allows for irrigation of the tissue to prevent drying during surgery.
It is known in the prior art to draw the commissure posts inward to contain and isolate the leaflets during the suturing process. However, structure utilized to create this feature may interfere with visibility in some prior art designs.
Kinks and cross over of the holder sutures increases the force needed to pull the holder sutures free after valve attachment. Pulling with a large force on the holder to release the valve after attachment to the patient may cause paravalvular leakage.
Applying too much tension on the holder sutures may cause a break in the holder suture. If the holder suture break occurs in an undesirable location, a suture remnant could be left in the patient when the physician subsequently cuts the holder suture to release the valve from the holder.
Commercial examples of heart valves include the Medtronic Mosaic® and Hanckock® II Aortic valves. Commercially available holder systems include the Cinch™ Advanced Implant System available from Medtronic of Minneapolis, Minn. Holders and packaging for heart valves are disclosed in U.S. Pat. Nos. 4,211,325; 4,865,600; 5,476,510; 5,716,401; 6,126,007; 6,338,740; 6,409,758; 6,558,418; 6,702,852; 6,736,845; 6,964,682; 6,966,925 and published U.S. patent application Ser. Nos. 2002-0082686-A1, 2003-0125805-A1; 2004-0138741-A1, 2004-0024451-A1; 2004-0148018-A1; and GB publication Nos. 2,108,393 and 2,011,259.